Defect Engineering in Bimetallic NiFe-BTC for Boosting Electrocatalytic Oxygen Evolution Reaction through Coordinated Ionic Liquids

Coordinatively unsaturated metal (CUM) sites in metal organic frameworks (MOFs) have demonstrated distinct catalytic activities, yet remain great challenges in their designing and engineering. Herein, a novel "Coordination Geometric Hindrance" approach based on ionic liquids (ILs) is proposed for defects construction in bimetallic MOF, of which the steric effect of competitively coordinated anions of imidazole ILs ([EMIM]X) enables the interference with the ordered growth of bimetallic NiFe-MOFs. Specifically, the PF6- anion displays the strongest binding energy with metals Ni and Fe, accordingly, facilitates the formation of CUM sites in NiFe-BTC/IL-PF6. Taking both advantages of CUM defects and good intrinsic conductivity of IL, NiFe-BTC/IL-PF6 achieves a superior electrocatalytic performance in the oxygen evolution reaction (OER), with the overpotential as low as 210 mV at 10 mA cm(-2), and the Tafel slope of 103 mV dec(-1), thus, giving an 18-fold larger TOF of the commercial OER catalyst of RuO2.